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Role of neuronal nitric oxide synthase in regulating retinal blood flow during flicker-induced hyperemia in cats.
- Source :
-
Investigative ophthalmology & visual science [Invest Ophthalmol Vis Sci] 2015 May; Vol. 56 (5), pp. 3113-20. - Publication Year :
- 2015
-
Abstract
- Purpose: To investigate how neuronal nitric oxide synthase (nNOS) contributes to regulation of the retinal circulation during rest and flicker stimulation in cats.<br />Methods: Using laser Doppler velocimetry, we measured the vessel diameter and blood velocity simultaneously and calculated the retinal blood flow (RBF) in feline first-order retinal arterioles. After intravitreal injections of Nω-Nitro-L-arginine methyl ester (L-NAME), a nonselective NOS inhibitor, and Nω-propyl-L-arginine (L-NPA), a selective nNOS inhibitor, we continuously monitored the retinal circulation without any perturbations for 2 hours. We then examined the changes in the RBF in response to 16-Hz flicker stimuli for 3 minutes at 2 hours after intravitreal injection of phosphate-buffered saline (PBS) as a control, L-NAME, L-NPA, and thromboxane A2 (TXA2) analogue U46619 as a basal tone-adjusted control.<br />Results: After intravitreal injection of L-NAME and L-NPA, the baseline RBF decreased gradually in a dose-dependent manner. In the PBS group, the RBF increased gradually and reached a maximal level after 2 to 3 minutes of flicker stimuli. After 3 minutes of 16-Hz flicker stimuli, the RBF increased by 53.5% ± 3.4% compared with baseline. In the L-NAME and L-NPA groups, the increases in RBF during flicker stimulation were attenuated significantly compared with the PBS group. In the TXA2 group, the reduction in the flicker-induced increase in RBF was comparable to that in the PBS group.<br />Conclusions: The current results suggested that increased RBF in response to flicker stimulation may be mediated by nitric oxide (NO) production via nNOS activation.
- Subjects :
- Animals
Arginine analogs & derivatives
Arginine pharmacology
Blood Flow Velocity physiology
Cats
Enzyme Inhibitors pharmacology
Female
Hemodynamics
Intravitreal Injections
Laser-Doppler Flowmetry
Male
NG-Nitroarginine Methyl Ester pharmacology
Nitric Oxide Synthase Type I antagonists & inhibitors
Photic Stimulation
Retina radiation effects
Hyperemia physiopathology
Nitric Oxide Synthase Type I physiology
Regional Blood Flow physiology
Retinal Vessels physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1552-5783
- Volume :
- 56
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- Investigative ophthalmology & visual science
- Publication Type :
- Academic Journal
- Accession number :
- 25783603
- Full Text :
- https://doi.org/10.1167/iovs.14-15854